Blood Supply to the Brain Flashcards
What is different about arteries in the brain?
Thin-walled so are easily blocked or ruptured
What is different about veins in the brain?
Have no valves, are thin-walled and have no muscles or elasticity
What does the internal carotid artery terminate as?
The anterior cerebral and middle cerebral arteries
What connects the two anterior cerebral arteries?
Anterior communicating arteries
What are the 4 main branches of the internal carotid artery?
Ophthalmic, posterior communicating, middle cerebral and anterior cerebral arteries
What does the ophthalmic artery supply?
Goes to the orbit and retina and also connects to the external carotid artery
What is the role of the posterior communicating artery?
Connects the carotid and vertebral artery systems (anterior and posterior circulation)
What is the role of the middle cerebral artery?
Supplies the basal ganglia, internal capsule and lateral 2/3rds of the cortex
What is the role of the anterior cerebral artery
Supplies the internal capsule, medial side of frontal and parietal lobes and anastomoses with the middle cerebral artery
Describe the passage of the vertebral arteries
Ascend through transverse foramina of C1-6 vertebrae and enter the cranium via the foramen magnum and unite with the contralateral vertebral arteries at the posterior pons to form the basilar artery
What forms the posterior circulation to the brain?
Vertebral arteries, basilar artery and posterior cerebral artery
What do the vertebral arteries supply?
Spinal cord and the dorsal medulla of the brainstem (via the PICA branch)
What does the basilar artery supply?
Pons and cerebellum
What does the posterior cerebral artery supply?
The inferior and medial aspects of the temporal and occipital cortex as well as the thalamus, midbrain and posterior internal capsule and anastomoses with the middle cerebral artery
What is the Circle of Willis?
Circle of cerebral arteries composed of: anterior communicating artery, anterior cerebral arteries, internal carotid arteries, posterior communicating arteries and posterior cerebral arteries
Which areas of the brain are supplied by the anterior cerebral artery?
Medial and superior brain as well as the frontal pole
Which areas of the brain and supplied by the middle cerebral artery?
Lateral brain and temporal pole
Which areas of the brain are supplied by the posterior cerebral artery?
Inferior brain and occipital pole
Where do all venous sinuses drain?
Internal jugular vein
Describe the venous drainage of the brain
Superficial cerebral veins cross the subarachnoid space and pierce the dura
What is the function of arachnoid granulation?
Allow CSF to flow into venous blood of the sinuses but prevent the backflow of blood into the sub-arachnoid space
What is the cavernous sinus?
A large collection of thin-walled veins and it is the only place where an artery travels through a venous structure.
What is the main blood supply to the spinal cord?
Great segmental medullary artery (Artery of Adamkiewicz)
What are the risk factors for stroke?
Atherosclerosis, hypertension, aneurysm, age, head injury, alcoholism, atriovenous malformation
What happens if there is damage to the middle cerebral artery in the dominant hemisphere?
Dominant hemisphere is often the left side (in right-handed people) and therefore there would be global aphasia (loss of speaking functionality) and sensorimotor loss on contralateral face, upper limb and trunk
What happens if there is damage to the middle cerebral artery in the non-dominant hemisphere?
Causes neglect syndrome, where they can no longer perceive information inputting on one side of their body
What happens if there is damage to the anterior cerebral artery?
Contralateral sensorimotor loss below the waist, urinary incontinence, personality deficits and ‘split-brain syndrome’ where there is difficulty conveying information across hemispheres due to inability to cross the corpus callosum
What happens if there is damage to the posterior cerebral artery?
Contralateral homonymous hemianopia, reading and writing deficits and impaired memory
What is lateral medullary syndrome?
Affects the posterior inferior cerebellar artery and there is sudden onset of symptoms including: nausea, dysphonia (hoarse voice), contralateral loss of pain and temperature sensation in body, ipsilateral loss of pain and temperature in the face, loss of gag reflex and presence of ipsilateral Horner syndrome
What are TIAs?
Transient ischaemic attacks which involved a temporary loss of brain function (less than 30 minutes) which has a sudden onset but is resolved within 24 hours
What are the branches of the external carotid artery?
- Superior thyroid
- Ascending pharyngeal
- Lingual
- Facial
- Occipital
- Posterior auricular
- Superficial Temporal
- Maxillary
Where does the common carotid artery bifurcate?
Splits into external and internal at the level of the superior border of thyroid
